1. Field of the Invention
The present invention relates to a method of converting audio data encrypted for anti-piracy and copyright protection to a suitable format to be played in a portable device, such as an MP3 player, and reproducing the converted audio data.
2. Background of the Related Art
Newly developed portable audio devices, such as an MP3 player, are very popular. An MP3 player is able to decode MP3-formatted digital audio file stored in a flash memory to produce high-quality sounds. Further, most MP3 players have interfacing function of communicating with a personal computer (PC). Accordingly, after a user obtains MP3 audio files from Web sites, with or without a fee, through Web surfing and downloading processes, the user stores the obtained MP3 files from a PC in an internal memory of an MP3 player through the interfacing function.
The digital audio data that are usually conveyed through a network, such as the Internet, are heavily encrypted through Digital Right Management (DRM) system to protect copyright.
Generally, decrypting such heavily-encrypted audio data requires a high computing power, and only after decryption, the data can be played by a device of much lower computing power than a conventional PC. The data can not be played by a portable device because a portable device, of which computing power is relatively low, can not conduct decrypting and decoding operation simultaneously in real time.
Accordingly, for listening to such heavily-encrypted audio data with a portable device, the following sequential steps should be performed: decryption of heavily-encrypted audio data with a PC; light or no re-encryption of the decrypted audio data; and transmission of the lightly-encrypted or non-encrypted audio data to a portable device.
Furthermore, the portable audio device has an equalizing function in general to improve fidelity of music listening. However, in the portable audio device with equalizing function, an equalizing mode suitable to a certain music genre is not set automatically. A user must select one of several equalizing modes believed proper for the present music to be played or adjust manually an individual amplifying gain for each band.
Needless to say, such selection and adjustment for each music is very tedious, and most users do not use equalizing function embodied in the portable audio device. As a result, music does not get conveyed to a listener authentically.